# Light in semi-cylinder

Monochromatic lights A and B are entered at points p and q, respectively, on the cross section of a semi-cylinder glass, as shown above left. Point O is the center of the cross section of the semi-cylinder glass. As shown above right, the paths of A and B are parallel, and they meet the curved surface of the semi-cylinder glass with angles $$\theta_A$$ and $$\theta_B$$, respectively, which are the critical angles of the two monochromatic lights. Which of the following statements is correct?

The refractive index of the air is $$1$$.

a) The wavelength of light A in the glass is longer than that of light B in the glass.
b) If the monochromatic light A enters at point q instead of p, then it will totally be reflected internally.
c) If a light with a shorter wavelength than the monochromatic light A is entered at point p, then it will totally be reflected internally.

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